1. Field of the Invention
The present invention relates to a vertical internal combustion engine having a crankshaft directed substantially in a vertical direction, particularly to a lubricating oil cooling structure in such a vertical internal combustion engine for an outboard motor.
2. Description of the Related Art
In an outboard motor disclosed in Japanese Laid-Open Utility Model Publication 63-164508, an outer wall of an oil pan is cooled by cooling water discharged after passing a thermostat to cool lubricating oil. Cooling of neighborhood of cylinders of the engine is not harmed by this, because the cooling water discharged after passing the thermostat is used.
However, sometimes it is required to cool lubricating oil more effectively by other means. In such a case, a device for cooling the lubricating oil not influencing a cooling water jacket in a neighborhood of a cylinder and a cooling water jacket in a neighborhood of an exhaust passage of high temperature. Therefore, the present invention aims for providing a lubricating oil cooling structure adapted for cooling lubricating oil more positively independently of cooling of the neighborhood of the cylinder.